In the field of grinding machines, in particular internal grinding machines for grinding workpieces of revolution, it is necessary to incorporate in the machine tool a slide movement for axially moving the grinding wheel into the bore area and thereafter, providing a radial feed movement to the grinding wheel to accomplish the grinding operation on the workpiece. Many types of compound slide systems have been developed in the prior art and are useful for providing the coordinate movement necessary during the grinding cycle, but several recently patented mechanisms have been developed for grinding machines, which greatly minimize the dependency on flat way slides for an internal grinding machine. The grinding machine shown in U.S. Pat. No. 4,096,667 (1978) illustrates a mechanism wherein a pair of parallel spaced bars are employed to provide the axial slide movement along the bar axis for presenting the grinding wheel into the bore of a workpiece. Subsequently, the radial feed movement is provided by pivoting the grinding wheel mount about the journal axis of a first bar, by radially displacing the second support bar from its normal position, thus tilting the grinding wheel support table and causing radial feed movement of the grinding wheel with respect to the workpiece. The radial displacement of the secondary support bar is accomplished by an elevating screw and nut assembly which is powered by a prime mover stepping motor, wherein all modes of feed are accomplished by the screw system. To accomplish very fine movement of the screw and nut combination, and thus proportional movement of the grinding wheel with respect to the workpiece, very large reduction mechanisms must be employed, such as worm and worm wheel drives off the prime mover to the feed screw. Further, the rigidity of the feed mechanism is solely dependent on the elevating screw and respective support bearings.
Applicant has obviated several infirmities in the foregoing design by providing a feed mechanism capable of very fine resolution output from a relatively coarsely controlled input motion. Further, applicant has provided a relatively stiff support for a secondary bar of such a twin bar support system.